You did nothing wrong This is unintended and regrettable behavior, and we apologize This is what the message should be. Maybe. I'd rather the software I use

You did nothing wrong This is unintended and regrettable behavior, and we apologize This is what the message should be. Maybe. I'd rather the software I use be apologetic than attempt to be my friend. That said, I'd settle for "we goofed, sorry" So it's not so much the tone (casual), but the content (own your defect, don't commiserate).